Changes in electrical and microstructural properties of microcrystalline cellulose as function of carbonization temperature

• Published in: Carbon (New York) Vol. 48; no. 4; pp. 1012 - 1024
• Main Authors: Rhim, Yo-Rhin, Zhang, Dajie, Fairbrother, D. Howard, Wepasnick, Kevin A., Livi, Kenneth J., Bodnar, Robert J., Nagle, Dennis C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.04.2010; Elsevier
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Materials science; Physics; Specific materials; Polarization; Oxygen; Electrical conductivity; Electrical properties; Growth; Cellulose; Carbon; Conversion; Heat treatments; Carbonization; Electrical measurement; Chemical decomposition; Frequency; Percolation; Electrons; Functional group
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/j.carbon.2009.11.020

AC and DC electrical measurements were made to better understand the thermal conversion of microcrystalline cellulose to carbon. This study identifies five regions of electrical conductivity that can be directly correlated to the chemical decomposition and microstructural evolution of cellulose during carbonization. In Region I (250–350 °C), a decrease in overall AC conductivity occurs due to the loss of the polar oxygen-containing functional groups from cellulose molecules. In Region II (400–500 °C), the AC conductivity starts to increase with heat treatment temperature due to the formation and growth of conducting carbon clusters. In Region III (550–600 °C), a further increase of AC conductivity with increasing heat treatment temperature is observed. In addition, the AC conductivity demonstrates a non-linear frequency dependency due to electron hopping, interfacial polarization, and onset of a percolation threshold. In Region IV (610–1000 °C), a frequency independent conductivity (DC conductivity) is observed and continues to increase with heat treatment due to the growth and further percolation of carbon clusters. Finally in Region V (1200–2000 °C), the DC conductivity reaches a plateau with increasing heat treatment temperature as the system reaches a fully percolated state.